Abnormality determination apparatus for internal combustion engine

ABSTRACT

An abnormality determination apparatus for an internal combustion engine in which an intake passage upstream of a supercharger and a crankcase are connected by a breather line includes: an intake flow rate detection unit that detects an intake flow rate in the intake passage; and an abnormality determination unit that determines abnormality of the breather line. The abnormality determination unit accumulates a time for which a rotation second-order component of a fluctuation waveform of the intake flow rate is equal to or more than a threshold over a predetermined period of time and determines the abnormality of the breather line when the accumulated value is less than a predetermined accumulation threshold.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2019-021331, filed Feb. 8, 2019,entitled “Abnormality Determination Apparatus for Internal CombustionEngine.” The contents of this application are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The present disclosure relates to an abnormality determination apparatusfor an internal combustion engine in which an intake passage upstream ofa supercharger and a crankcase are connected by a breather line.

BACKGROUND

Such an abnormality determination apparatus for an internal combustionengine is described as a second embodiment in Japanese Unexamined PatentApplication Publication No. 2017-078378. In such a case where theconnection portion of the breather line to the intake passage has comeoff, the connection portion serves as an opening end portion for the aircolumn of the intake passage, thus causing the resonant frequency of theair column to change. Focusing on this fact, this abnormalitydetermination apparatus for an internal combustion engine monitors themagnitude of the pulsation of the intake flow rate in the intake passageto determine whether the connection portion of the breather line hascome off.

In the above-described conventional abnormality determination apparatus,if the load on the internal combustion engine temporarily fluctuates dueto disturbance or the like, the pulsation of the intake flow ratefluctuates to a large extent. For this reason, there is a possibilitythat the above-described conventional abnormality determinationapparatus erroneously determines whether the connection portion of thebreather line has come off.

SUMMARY

It is desirable to precisely determine the abnormality of a breatherline of an internal combustion engine without being affected bydisturbance or the like.

A first aspect of the disclosure proposes an abnormality determinationapparatus for an internal combustion engine in which an intake passageupstream of a supercharger and a crankcase are connected by a breatherline, including: an intake flow rate detection unit that detects anintake flow rate in the intake passage; and an abnormality determinationunit that determines abnormality of the breather line, wherein theabnormality determination unit accumulates a time for which a rotationsecond-order component of a fluctuation waveform of the intake flow rateis equal to or more than a threshold over a predetermined period of timeand determines the abnormality of the breather line when the accumulatedvalue is less than a predetermined accumulation threshold.

According to the configuration of the first aspect, it is possible toprecisely determine the abnormality of the breather line based on therotation second-order component of the fluctuation waveform of theintake flow rate, which is unlikely to be affected by fluctuation inload on the internal combustion engine due to disturbance or the like.

A second aspect of the disclosure proposes an abnormality determinationapparatus for an internal combustion engine in which in addition to theconfiguration of the first aspect, the rotation second-order componentis calculated by multiplying the fluctuation waveform of the intake flowrate by a sine wave and a cosine wave corresponding to an angularvelocity of a crank, followed by integration.

According to the configuration of the second aspect, it is possible toeasily calculate the rotation second-order component of the fluctuationwaveform of the intake flow rate.

Note that an air flow meter 16 in an embodiment corresponds to theintake flow rate detection unit of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the disclosure will become apparent in the followingdescription taken in conjunction with the following drawings.

FIG. 1 is a diagram illustrating the configuration of an internalcombustion engine including an abnormality determination apparatus for abreather line of one embodiment.

FIG. 2 is a block diagram of the abnormality determination apparatus forthe breather line of one embodiment.

FIGS. 3A and 3B are explanatory diagrams for change in position of apiston associated with the rotation of a crankshaft of one embodiment.

FIG. 4 is an explanatory diagram of procedure of determining abnormalityof the breather line of one embodiment.

FIG. 5 describes bandpass filter for extracting only the rotationsecond-order component from the fluctuation in the intake flow rate inthe intake passage.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the disclosure will be described based onFIGS. 1 to 4.

As illustrated in FIG. 1, on an intake passage 12 of an in-linefour-cylinder 4-cycle internal combustion engine 11 to be mounted on anautomobile, disposed are: an air cleaner 15, which removes dust inintake air; an air flow meter 16, which measures the intake flow rate; asupercharger 17 composed of a turbocharger or a supercharger, whichpressurizes the intake air; and a throttle valve 18, which adjusts theintake flow rate by narrowing the intake passage 12, in this order froman inlet 13 at the upstream end in the flow direction of the intake airtoward an intake manifold 14 at the downstream end in the flow directionof the intake air. A portion of the intake passage 12 between the airflow meter 16 and the supercharger 17 and a crankcase 19 of the internalcombustion engine 11 are connected by a breather line 20. The intakemanifold 14 and the crankcase 19 of the internal combustion engine 11are connected by a positive crankcase ventilation (PCV) line 21, and amiddle portion of the PCV line 21 is opened and closed by a PCV valve22.

Part of the fuel component contained in the intake air flows from thecombustion chamber of the internal combustion engine 11 into thecrankcase 19 through a gap between a piston and a cylinder as a blow-bygas, which is returned to the intake passage 12 through the breatherline 20 or is returned to the intake passage 12 through the PCV line 21.The fuel component contained in the blow-by gas is thus prevented frombeing released to the atmosphere.

Specifically, when the PCV valve 22 is opened during natural aspirationin which the supercharger 17 is not activated, the atmospheric pressureacts on the intake passage 12 upstream of the throttle valve 18 whilethe intake negative pressure of the internal combustion engine 11 actson the intake passage 12 downstream of the throttle valve 18. Hence, theintake air in the intake passage 12 upstream of the throttle valve 18flows through the breather line 20 into the crankcase 19. From thecrankcase 19, the intake air together with the blow-by gas is returnedinto the intake manifold 14 through the PCV line 21. The blow-by gastogether with the intake air is eventually supplied into the combustionchamber of the internal combustion engine 11.

Moreover, at the time of supercharging in which the supercharger 17 isactivated, the supercharging pressure acts on the intake passage 12downstream of the supercharger 17. Once the PCV valve 22 is closed, thesupercharging pressure is prevented from escaping through the PCV line21 into the crankcase 19. The blow-by gas in the crankcase 19 is suckedout into the intake passage 12 by the negative pressure generatedupstream of the activated supercharger 17. From the intake passage 12,the blow-by gas together with the intake air is supplied into thecombustion chamber of the internal combustion engine 11 through theintake passage 12.

In a case where during the supercharging of the internal combustionengine 11, a first connection portion 23 at which the breather line 20is connected to the intake passage 12 comes off or a second connectionportion 24 at which the breather line 20 is connected to the crankcase19 comes off, the blow-by gas flowing through the breather line 20 fromthe crankcase 19 toward the intake passage 12 is possibly released tothe atmosphere. For this reason, it is necessary to detect suchabnormality of the breather line 20 and issue an alert.

As illustrated in FIG. 2, to an abnormality determination unit 30 formedof an electronic control unit that determines abnormality of thebreather line 20, the air flow meter 16 and an alert unit 32 areconnected. The alert unit 32 is formed of a liquid crystal panelprovided on an instrument panel, for example.

Next, the action of the embodiment including the above-describedconfiguration will be described.

As illustrated in FIG. 3A, a piston 33 of the internal combustion engine11 is connected to a crankshaft 35 by a connecting rod 34. The height ofthe piston 33 (the position in the direction of movement of the piston33) changes as a function of the rotational position of the crankshaft35 and the oscillation position of the connecting rod 34. That is, thefluctuation in the height of the piston 33 attributable to the rotationof the crankshaft 35 is a rotation first-order fluctuation in which theheight fluctuates once per revolution of the crankshaft 35. On the otherhand, the fluctuation in the height of piston 33 attributable to theoscillation of the connecting rod 34 is a rotation second-orderfluctuation in which the height fluctuates twice per revolution of thecrankshaft 35.

As illustrated in FIG. 3B, in the in-line four-cylinder 4-cycle internalcombustion engine 11, the pistons 33 of the #1 cylinder and the #4cylinder operate at the same phase while the pistons 33 of the #2cylinder and the #3 cylinder operate at a different phase shifted by180° from the above phase. Hence, the internal pressure fluctuation ofthe crankcase 19 attributable to the oscillations of the four connectingrods 34 is a rotation second-order fluctuation in which the internalpressure fluctuates twice per revolution of the crankshaft 35.

When the rotation second-order fluctuation is generated in the internalpressure of the crankcase 19 as described above, the pressurefluctuation is transmitted to the intake passage 12 through the breatherline 20, causing the rotation second-order fluctuation in the intakeflow rate in the intake passage 12. The present embodiment is configuredto determine the abnormality of the breather line 20 based on therotation second-order fluctuation in the intake flow rate generated inthe intake passage 12.

Note that the number of cylinders of the internal combustion engine 11to which the embodiment is applied is not particularly limited. However,in a V-type 6-cylinder internal combustion engine, the pressurefluctuations in the internal pressure of the crankcase 19 due to themovements of 6 pistons 33 cancel out, so that the fluctuations in theinternal pressure of the crankcase 19 are relatively small. Hence, thepresent disclosure is favorably applicable to the in-line four-cylinderinternal combustion engine 11.

Next, the procedure of determining the abnormality of the breather line20 will be described based on FIG. 4.

The determination of the abnormality of the breather line 20 of thepresent embodiment is executed when the flow rate of the intake airdetected by the air flow meter 16 is a predetermined value or more andthe internal combustion engine 11 is being operated with a load of apredetermined value or more. This is because when the internalcombustion engine 11 is being operated with a small load, thefluctuation in the intake flow rate in the intake passage 12 is small,making it difficult to obtain the amount of fluctuation necessary todetermine abnormality with high precision.

First, in Step S1, the fluctuation in the intake flow rate in the intakepassage 12 is detected by the air flow meter 16. As described above, aperiodic pressure fluctuation is generated in the crankcase 19 by themovement of the piston 33. This periodic pressure fluctuation istransmitted to the intake passage 12 through the breather line 20connected to the crankcase 19, generating the fluctuation in the intakeflow rate. The fluctuation in the intake flow rate in the intake passage12 contains the rotation first-order component, the rotationsecond-order component, and rotation third-order and higher-ordercomponents. However, since the rotation third-order and higher-ordercomponents are small, the rotation first-order component and therotation second-order component are dominant.

In subsequent Step S2, only the rotation second-order component in thefluctuation in the intake flow rate in the intake passage 12 isextracted using a bandpass filter.

The principle of the bandpass filter for extracting only the rotationsecond-order component from the fluctuation in the intake flow rate inthe intake passage 12 will be described below.

As illustrated in FIG. 5 ([Math. 1]), if a value obtained by multiplyinga certain fluctuation waveform of the intake flow rate in the intakepassage 12 detected by the air flow meter 16 by the second-order sinewave is added for each phase, the X component of the rotationsecond-order component of the certain waveform is obtained. If a valueobtained by multiplying the certain waveform by the second-order cosinewave is added for each phase, the Y component of the rotationsecond-order component of the certain waveform is obtained.

To be more specific, the certain waveform f(t) may be expressed as[Math. 2], summation of sine waves sin(ωt), sin(2ωt), sin(3ωt), . . .and cosine waves cos(ωt), cos(2ωt), cos(3ωt), . . . in accordance withFourier series expansion. Here, the angular frequency ω has one cyclewith 720 deg corresponding to two rotations of the crankshaft 35.f=1+a ₁ sin(ωt)+b ₁ cos(ωt)+a ₂ sin(2ωt)+b ₂ cos(2ωt)+ . . .  [Math. 2]

When the [Math. 2] is multiplied by the sine wave sin(ωt), followed byintegration, only the Fourier coefficient a1 of the angular frequencysine wave is left as shown in [Math. 3].

$\begin{matrix}{{\int{f \cdot {\sin\left( {\omega\; t} \right)} \cdot {dt}}} = {{\int{{\left( {1 + {a_{1}{\sin\left( {\omega\; t} \right)}} + {b_{1}\cos\;\left( {\omega\; t} \right)} + {a_{2}{\sin\left( {2\;\omega\; t} \right)}} + \ldots}\mspace{11mu} \right) \cdot \sin}\;{\left( {\omega\; t} \right) \cdot {dt}}}} = {{\int{\left( {{\sin\left( {\omega\; t} \right)} + {a_{1}{{\sin\left( {\omega\; t} \right)} \cdot {\sin\left( {\omega\; t} \right)}}} + {b_{1}{{\cos\left( {\omega\; t} \right)} \cdot {\sin\left( {\omega\; t} \right)}}} + {a_{2}{{\sin\left( {2\;\omega\; t} \right)} \cdot \;{\sin\left( {\omega\; t} \right)}}} + \ldots}\mspace{11mu} \right) \cdot {dt}}} = {{\int{{\sin\left( {\omega\; t} \right)} \cdot {dt}}}{\quad^{= 0}{{{+ {\int{a_{1}{{\sin\left( {\omega\; t} \right)}^{2} \cdot {dt}}}}} + {{{{\int{b_{1}{{\cos\left( {\omega\; t} \right)} \cdot {\sin\left( {\omega\; t} \right)} \cdot {dt}}}} + {\int{a_{2}\sin\;{\left( {2\;\omega\; t} \right) \cdot {dt}}}} + \ldots}\mspace{11mu}}{\quad}^{= 0}}} = {\pi\; a_{1}}}}}}}} & \left\lbrack {{Math}.\mspace{14mu} 3} \right\rbrack\end{matrix}$

Similarly, when the [Math. 2] is multiplied by the cosine wave cos(ωt),followed by integration, only the Fourier coefficient b1 of the angularfrequency cosine wave is left. It is thus possible to easily obtain therotation second-order component of the certain waveform f(t) from theseFourier coefficients a1 and b1.

Once the rotation second-order component in the fluctuation in theintake flow rate in the intake passage 12 is extracted in Step S2 asdescribed above, a time T for which a peak portion of the rotationsecond-order component in the fluctuation in the intake flow rate in theintake passage 12 is equal to or more than a predetermined threshold isaccumulated over a predetermined period of time (for example, 2 to 10seconds) in Step S3. If the accumulated value is equal to or more thanan accumulation threshold, the breather line 20 is determined to benormal. If the accumulated value is less than the accumulationthreshold, the breather line 20 is determined to be abnormal and thealert unit 32 is activated to notify a passenger of that effect.

The reason why it is possible to determine whether the breather line 20is normal or abnormal from the accumulated value of the time T for whichthe rotation second-order component in the fluctuation in the intakeflow rate in the intake passage 12 is equal to or more than thepredetermined threshold is as described below. In a case where thebreather line 20 is normal and is not in communication with theatmosphere, the pressure fluctuation of the crankcase 19 is transmittedas it is to the intake passage 12 from the breather line 20 and theresulting fluctuation in the intake flow rate in the intake passage 12is detected by the air flow meter 16. Hence, if the detected fluctuationin the intake flow rate in the intake passage 12 is large, that is, ifthe peak portion of the intake flow rate is equal to or more than thethreshold, it is possible to determine that the breather line 20 is notin communication with the atmosphere and is normal. On the other hand,if the breather line 20 has come off the first or second connectionportion 23 or 24 or is broken in a middle thereof, the breather line 20communicates with the atmosphere and the fluctuation in the intake flowrate in the intake passage 12 is reduced. Hence, if the detectedfluctuation in the intake flow rate is small, that is, if the peakportion of the intake flow rate is likely to be less than the threshold,it is possible to determine that the breather line 20 is incommunication with the atmosphere and is abnormal.

Meanwhile, consider a case where the magnitude of the fluctuation in theintake flow rate in the intake passage 12 is evaluated. If the intakeflow rate fluctuates to a positive value and a negative value, merelyaccumulating the intake flow rate over a predetermined period of timeresults in incorrect evaluation because the positive and negative valuescancel out. In view of this, as in the present embodiment, accumulatingthe time T for which the peak portion of the fluctuation in the intakeflow rate is equal to or more than the predetermined threshold over thepredetermined period of time makes it possible to correctly evaluate themagnitude of the fluctuation in the intake flow rate and conduct theabnormality determination with high precision.

In addition, if the load on the internal combustion engine 11 fluctuatesdue to disturbance or the like, the rotation first-order component ofthe fluctuation in the intake flow rate in the intake passage 12 alsofluctuates. However, since the rotation second-order component is hardlyaffected, it is possible to increase the determination precision andprevent erroneous determination from occurring by conducting theabnormality determination on the breather line 20 base on the rotationsecond-order component.

Although the embodiment of the disclosure has been described so far,various modifications in design may be made without departing from thescope of the disclosure.

For example, the number of cylinders of the internal combustion engine11 is not limited to the four in the embodiment.

Moreover, although the breather line 20 is connected to the crankcase 19in the embodiment, it is also possible to achieve the advantageouseffect of the disclosure by causing the internal space of the crankcase19 and the internal space of a head cover to communicate and connectingthe breather line 20 to the head cover. Hence, an embodiment in whichthe breather line 20 is connected to another space that communicateswith the crankcase 19 is also encompassed by the scope of thedisclosure. Although a specific form of embodiment has been describedabove and illustrated in the accompanying drawings in order to be moreclearly understood, the above description is made by way of example andnot as limiting the scope of the invention defined by the accompanyingclaims. The scope of the invention is to be determined by theaccompanying claims. Various modifications apparent to one of ordinaryskill in the art could be made without departing from the scope of theinvention. The accompanying claims cover such modifications.

What is claimed is:
 1. An abnormality determination apparatus of aninternal combustion engine in which an intake passage located upstreamof a forced-induction system and a crankcase are connected by a breatherline, comprising: an intake flow rate detection detector that detects anintake flow rate in the intake passage; and an abnormality determinationunit that determines abnormality of the breather line, wherein theabnormality determination unit: determine a length of time T duringwhich a rotation second-order component of a fluctuation waveform of theintake flow rate is equal to or more than a threshold for each peak influctuation of the rotation second-order component over a predeterminedperiod of time, accumulates the length of time T to obtain anaccumulated value of length of time, and determines occurrence of theabnormality of the breather line when the accumulated value is less thana predetermined accumulation threshold, wherein the rotationsecond-order component of the fluctuation waveform of the intake flow isa fluctuation waveform which fluctuates twice per revolution of acrankshaft of the internal combustion engine.
 2. The abnormalitydetermination apparatus of an internal combustion engine according toclaim 1, wherein the rotation second-order component is calculated bymultiplying the fluctuation waveform of the intake flow rate by a sinewave and a cosine wave corresponding to an angular velocity of a crankof the engine, followed by integration.
 3. The abnormality determinationapparatus of an internal combustion engine according to claim 1, whereinthe rotation second-order component represents a rotation second-orderfluctuation generated in an internal pressure of the crankcase.
 4. Anabnormality determination method of an internal combustion engine inwhich an intake passage located upstream of a forced-induction systemand a crankcase are connected by a breather line, the method comprisingsteps of: detecting by a detector an intake flow rate in the intakepassage; determining by a computer a length of time T during which arotation second-order component of a fluctuation waveform of the intakeflow rate is equal to or more than a threshold for each peak influctuation of the rotation second-order component over a predeterminedperiod of time accumulating by a computer the length of time T to obtainan accumulated value of length of time; and determining by the computeroccurrence of the abnormality of the breather line when the accumulatedvalue is less than a predetermined accumulation threshold, wherein therotation second-order component of the fluctuation waveform of theintake flow is a fluctuation waveform which fluctuates twice perrevolution of a crankshaft of the internal combustion engine.
 5. Theabnormality determination method of an internal combustion engineaccording to claim 4, wherein the step of detecting the intake flow ratein the intake passage is performed during the forced-induction system isactivated.
 6. An abnormality determination apparatus of an internalcombustion engine in which an intake passage located upstream of aforced-induction system and a crankcase are connected by a breatherline, comprising: an intake flow rate detection detector that detects anintake flow rate in the intake passage; and an abnormality determinationunit that determines abnormality of the breather line, wherein theabnormality determination unit: determine a length of time T duringwhich a rotation second-order component of a fluctuation waveform of theintake flow rate is equal to or more than a threshold for each peak influctuation of the rotation second-order component over a predeterminedperiod of time, accumulates the length of time T to obtain anaccumulated value of length of time, and determines occurrence of theabnormality of the breather line when the accumulated value is less thana predetermined accumulation threshold, wherein the rotationsecond-order component is calculated by multiplying the fluctuationwaveform of the intake flow rate by a sine wave and a cosine wavecorresponding to an angular velocity of a crank of the engine, followedby integration.